Reduction of organic nitro compounds



I i v UNITED sr cnAUnonY ALLAN was, or

tins.

Patented Sept. 20, 1932 EAST AURORA; new, YoItK, nssrenon 7rd narrower. H

ANILINE & CHEMICAL oonrnnv, or nnw vonx, 1V\T. "Y., A oonrona'rron on NEW YORK The present invention relates to the reduction of aromatic nitro compounds, and more particularly, to the reduction of metadinitro derivatives of aromatic hydrocarbons of the'benzene series for the production of the corresponding meta-nitroamino derivatives.

It is an objectof the invention toprovide a process for the reduction of a meta-dinitro derivative of an aromatic hydrocarbon by treatment with an alkali metal sulfide in the presence of an organic liquid as a solvent, wherein the solvent is recovered with minimum losses, and a better yield of a purer reduction product is obtained- Another object of the invention is the production of a pure meta-nitraniline by aprocess which is simple, efiicient and economical in its operation. 7

Other objects of the invention will inpart b gtobvious and will in part appear hereina er.

" The, invention accordingly comprises the severalsteps of the process herein disclosed and the relation of one ormore of such steps with respect to each ofthe others thereof, as will be exemplified in the 'following disclosure, and the scope of the [invention will be indicated in the claims.

In the reduction of m-dinitro derivatives of aromatic hydrooarbonaior example, metadinitrobenzene, by treatment with an alkali metal sulfide for the production of the corresponding .m-nitroamino compounds, it has heretofore been the procedure to carry out the reaction by gradually adding an aqueous solution of the alkali metal sulfide to a suspension or solution of'the meta-dinitro' derivative in water or in alcoholh As thus performed, the process gives; low yields of a reduction product of inferior purity. In commercial practice, the alcohol used in the process is recovered by distillation and rectification, whichhas the disadvantage thatit incurs losses of solvent and requires considerable time andlabor for. its performance.

In general, the crude reduction product resulting from either process must'be purified for use in the manufacture of dyestuffs.

' According to the present invention, it has been found that the reduction of meta-dinitro as of the alkali metals.

quality. of the reduction I is'addedtothe mixture-of the water and the solution of the 'dinitro compound in theor Application filed August 24,1;929. Serial No. 388,21'0.

derivatives of; the aromatic hydrocarbons by treatment with an alkali metal sulfide may be performed in the presence of a two phase liquid'system comprising water and an inert organic liquid which is substantially immiscible with water, the organic liquid'being a solvent for said dinitro derivative. Theor: ganic liquid employed is usually and preferably, 'althoughnot necessarily, a solvent for the nitroamino compound produced. The organic liquid employed is also preferably volatile in steam, and can therefore-be readily recovered with little, if any, loss and-further, no rectification is required to adapt it for reuse in the process. a

{Organic liquids which are suitable for use in the practice of the present invention are the chlorinated hydrocarbons, for example,

carbon tetrachloride, tetrachlorethane, chlor throughout the specification and claims, it is intended to include the hydrosulfides, sulfides, and polysulfides of ammonium as well 7 In the'practice olfthe present invention, the dinitro body is dissolved in the organic liquid, and to the resulting solution or mixture, while well agitated or stirred, an aque ous solution of the alkali metal sulfide. is added. Considerable heat is generated during the addition of the sulfide. If the temperature increases sufiiciently to boil the reaction 'mixture, the organicliquid may be permitted to distil oil, and may be condensed and collected, or it may be condensed and returned to the reduction mass. reduction is completed, the organic liquid remaining in the mixture is distilled off and collected, and thereduc'tion product is recovered from many suitable manner. A product of excellent purity can be thus obtained in ex celle-ntyields. 4 3 Y I Y Forthe best results, both as to yields and product, the sulfide When the I the residual aqueous liquors ganic liquid as quickly as operation conditions will permit, the temperature of the reaction mixture beingmaintained at or near its boiling point, but the order may be reversed and the organic liquid containing the m-dinitro compound may be added to the alkali metal sulfide solution. The time required for the addition of the sulfide will depend. n op rating. fa t rs such. as. the ize of the batch, the liquid, the concentration'of the reaction mass, the violence of agitation, etc.- Preferably, the sulfide employed is added in aqueous solution. It is also preferable that the organic liquid employedis one which boils at about 90 to 100 C. Preferably, the amount of organic. liquid employed is sufficient to dissolve most or all of. the dinitro. body and the total amount of water-present is sufficient to dissolve, when hot, the resultant nitroaminocompound: .As illustrative embodiments of the manner in which the process of the present invention may be practiced, the following examples are given. Theparts are by weight. 7

Example 1.-'Ajpolysulfide v(NaS solution is prepared by heating 180 grams of-a 7 per cent Na S solution with 10 grams flowers of sulfur.

25 grams of technical m-dinitrobenzene (85 per cent purity) and 40' grams solvent naphtha, are placed in a reactor equipped with an agitator and a reflux condenser. The mixture is warmed to about- O. until complete solution occurs; 1000 grams hotwater is then added. The m-dinitrobenzenesolw tion is heated to boiling '(about'9495 C.) and the hot polysulfide. solution is rapidly added thereto. The sulfide is all added within-a period o'fabout 2 minutes- The re action of the polysulfide generates enough heat to appreciably increase the rate of boil ing of the reaction mass.v Reduction of the m-dinitrobenzene to m-nitraniline takes place almost immediately. T The m-nitraniline may be isolatedin any suitable manner, for example, byfiltering the hot' solution to eliminate free sulfur, and distilling' off the solventnahptha withsteam; The m-nitraniline remains behind dissolved in theaqueous portion from which solution it crystallizes out on cooling, and is filtered and washed. The product thus obtainedis in the form of bright yellow crystals. Example Q.25. grams of technical m-di-, nitrobenzene (91 per cent purity),"60 grams of solvent naphtha and'900 grams water are combined and heated to a temperature of about 90-92 C. in a reactor equipped with a Liebig condenser. To this solution is add ed within a period of about 5'minutes, a polys'ulfide ('Na S solution prepared from 5.5 grams sulfur and 191 Na s solution.

volatility of the o ganic,

\ from which grams of a 7 percent. a The process is carried. out 7 according to example 1, except that the sol vent naphtha is permitted to distil off during the reaction. After the reaction is completed, any remaining solvent naphtha is steam distilled ofl and the free sulfur is filtered off from the hot solution. Upon cooling, the m-nitraniline crystallizes out of solution in the form of bright yellow crystals of exceptionally high purity, having a melting point of about 113.43 C. The yield is about 90 to 95 per cent. The product is usually sufficiently pure, without further purification, for use in making azo dyestuffs. In the'above examples, the aqueous portion the. m-nitraniline crystallizes out contains sodium thiosulfate which can be recovered in any suitable manner,-as by evaporating off. the water. By the use of an immiscible solvent of suitable boiling point, the reducing agentcanbe rapidly added, without producing excessive heating. 7 Further, the temperature is automatically prevented from rising too high by the evaporation of the solvent which may be refluxed or may bepermitted to distil off with the steam generated.

The process of the present invention is applicable to the reduction of pure or purified, as well as technical, dinitro derivatives with out substantially afi'ecting the yield or the quality of the final product. In place of metadinitrobenzene, other dinitro compoundsimay be reduced, forexample, the meta dinitro de, rivatives of toluene, xylene, etc. r I cla imz; P

1. In the producti0n of an aromatic nitro-.

amino derivative, the process which c0m= prises subjecting a meta dinitro derivative of a hydrocarbon of the benzene'series to the ac= tion of an alkali metalsulfide in the presence of water and of an-inert, Water immiscible or ganic liquid which is dinitro derivative.

2. In the production of meta-nitraniline, the process which comprises subjecting metadinitrobenzene to the action of an alkali metal sulfide in the presenceof water and of an inert, water immiscible organic liquid which is a solvent for the meta-dinitrobenzene.

3. In the reduction of meta-dinitrobenzene, the process which comprises quickly introducing a water-soluble sulfide into a heated mix-. ture of meta-dinitrobenzene and waterin' the presence of an inert, water immiscible organic hydrocarbon liquid which is a solvent for the m-dinitrobenzene.

4. The process which comprises dissolving m-dinitrobenzene in solvent naphtha, treating the solution with an aqueous sodium polysulfide solution to produce m-nitraniline, distilling off the solvent naphtha,-filtering the resulting aqueous solution of m-nitraniline, and crystallizing out the m-nitraniline from the filtered aqueous residue. Y

v 5. In thev production ofm-nitraniline by the reduction of m-dinitrobenzene with an:

a solvent for them alkali metal sulfide, the improvement which comprises carrying out the reduction in the presence of a two phase liquid system comprising water and an inert organic liquid which is substantially immiscible with water and in which organic liquid the m-dinitrobenzene is soluble.

6. In the production of a meta-nitro-amino compound by the reduction of a meta-dinitro derivative of a hydrocarbon of the benzene series with an alkali metal sulfide, the step which comprises carrying out the reaction in the presence of water and of an inert organic liquid which is a solvent for the dinitro body and which is substantially immiscible with water. I r

7. A process of preparing meta-nitraniline which comprises subjecting meta-dinitrobenzene dissolved in solvent naphtha to the acgim of an aqueous solution of a sodium sul- 8. The process which comprises dissolving m-dinitrobenzene in solvent naphtha, treating the solution with an aqueous sodium polysulfide solution to produce m-nitraniline, ex-

tracting the m-nitraniline with hot water as it is produced, distilling oil the solvent naphtha, filtering the resulting hotaqueous solution of m-nitraniline, and crystallizing out the m-nitraniline from the filtered aqueous residue.

9. In the production of meta-nitraniline by the reduction of meta-dinitrobenzene with an alkali metal sulfide, the improvement which comprises carrying out the reduction in the presence of a two phase liquid system comprising water and solvent naphtha.

h Ini witness whereof, I have hereunto set my an 40 CHAUNCEY ALLAN LYFORD. 

